In production of a molded article, such as a film, a sheet, a bottle or a fiber, made from a thermoplastic polymer as a raw material, the molded article is produced by adding to the material a functional organic compound such as an antioxidant, a thermal stabilizer, an ultraviolet ray absorbing agent or an antistatic agent and so on, and forming the mixture with a method such as an extrusion molding, a blow molding or an injection molding. Moreover, a molded product has been investigated which expresses a function by containing a functional compound, e.g., an odorous substance, an insecticide, a repellant or an antibacterial compound in a molded product and sustainedly releasing the functional compound from the molded product.
However, except for a plasticizer for vinyl chloride resin or a special example (Patent Document 1) in which an ethylene-vinyl acetate copolymer is swelled and contained with a solvent at a room temperature, a content of a liquid at a room temperature is remarkably small. As a compound other than the above examples, a liquid compound content, which can be contained in a general thermoplastic polymer, is limited in a range without a practical problem. And the state of such a liquid compound is not a droplet. Moreover, since the liquid compound is forcedly confined in the polymer as a phase separation state by melt-kneading process or others, the compound has no practical use because of a large amount of bleeding it out on a surface in a short period of time. On the other hand, a matter which contains a low content of a liquid compound disappears the liquid compound in such a short period of time as several weeks at most, and lacks a long-term duration of the function.
In order to aid diffusion of a volatile component to a surface, there is an example (Patent Document 2) which adds a hydrogenated diene-series polymer to a polypropylene to sustainedly release the volatile component. However, it is the self-evident truth that a disappearent rate of the volatile component increases as a diffusion rate is larger. Therefore, the above example is contradictory and is a theoretically impracticable proposal. Moreover, in the proposal, there is no description that the volatile component stably exists in the form of a liquid in a matrix polymer, and no description about compatibility between the additive and the matrix polymer at all.
A paint (or coating) includes a powdered paint and a liquid paint. As a powder coating for a thin film having about 50 μm, there are electrostatic spraying methods such as a corona system and a tribo system. In the corona system, a powder is electrostatically attached to a coated object by applying a high voltage (30-90 KV) on a corona pin provided with a tip of a gun for spraying the powder, and charging the powder (paint) released in the electric field between the pin and the object. In the tribo system, a powder is attached to a coated object by generating electrostatic charges with the friction between an inner wall of a gun and the powder when the powder passes through the inside of the gun.
A coated object to which a powdered paint is attached is baked in a furnace at 150 to 200° C. for 10 to 20 minutes so that the coating is finished. As a polymer component in the paint, thermoplastic and thermosetting polymers are used. The thermosetting polymer is often modified in an end thereof to enable combination use with a curing agent such as a urethane or epoxy curing agent.
As a powder coating method for coating a thick film, there are a fluidized bed coating method and an electrostatic spraying method. In the fluidized bed coating method a thermoplastic powdered paint is mainly used, and in an electrostatic spraying method a thermosetting powdered paint is mainly used. The fluidized bed coating method comprises suspending and floating of a powdered paint by a compressed air, and dipping of a pre-heated object to be coated in the floating paint. In this method, the floating paint is fused and adhered to the object to usually give a thick paint film by 200 to 500 μm thickness. The polymer for the thermoplastic powdered paint used in the fluidized bed coating method may include, for example, a polyvinyl chloride, a polyethylene, a polypropylene, a polyester, a nylon, and so on.
The generally used liquid paint is provided in an aqueous type and a solvent type. To such a liquid paint are blended a pigment, a dispersing agent (or dispersant), a stabilizer, a polymer, a crosslinking agent and others. The thickness of the film is 15 to 60 μm. Out of consideration to the environment, use of the aqueous type paint has increased. As the polymer to be blended, a thermoplastic or thermosetting polymer is used. For example, the polymer includes an alkyd polymer, an unsaturated polyester-series polymer, an epoxy-series polymer, a melamine-series polymer, an acrylic resin, a urethane-series polymer, a phenol-series polymer, a nylon-series polymer, an ester-series polymer, and a fluorocarbon resin.
The ship's bottom encrusted and fouled with extraneous matters such as a barnacle and so on increases friction with water, and is not economical in the running. For example, it has been suggested that an organic tin compound, copper oxide, mercury oxide, and others are used as an antifouling agent (Patent Documents 3 and 4). Moreover, in order to impart an antifouling property to a ship's bottom paint, an organic tin compound has been used by being mixed with the paint. However, since it has been known that an organic tin acts as an endocrine-disrupting chemical, such a compound has dropped out of use. Moreover, copper oxide and mercury oxide are also highly toxic compounds. On the other hand, many self polishing-type ship's bottom paints are commercially available. In these paints, it is considered that a fresh layer of the paint is constantly exposed by peeling off of the paint in the surface layer due to hydrolysis of the paint polymer, and decrease in the thickness of the paint film. However, since the ship's bottom is encrusted with the fouling matter until the surface layer peels off, it is inevitable that the effect of the paint is limited.
A highly safe antifouling agent may include an essential oil. The essential oil has been also used as a food additive over the years before Christ. However, the essential oil has intractability due to volatility. As a method for mixing a polymer and a volatile compound, there is a method which comprises allowing a porous powder such as a rubber component or a zeolite to contain a volatile component in advance, and mixing the resulting matter and the polymer temporarily. However, in such a method, although the polymer was temporarily allowed to contain the volatile component at a high concentration, it was difficult to sustainedly release the volatile component over a long period of time because of fast diffusion (or spread) of the volatile component. Further, the method had a shortcoming of increasing the diffusion rate as the surface area increases. Therefore, in a paint application for coating a large surface area with a thin film, the diffusion of the volatile component was fast.
Moreover, as an example for using a polymer having thermoplasticity in spite of containing water, there has been proposed a method which comprises mixing and allowing an inorganic substance (e.g., magnesium hydroxide, aluminum hydroxide and calcium silicate) to contain in the polymer, wherein the inorganic substance is in the form of a hydrate state (or has crystallization water) (Patent Document 5). However, since the crystallization water of the inorganic substance is released at a temperature as relatively high as 300 to 550° C., the method is disadvantageous in that the crystallization water does not act at a low temperature. It is impossible to allow the crystallization water to contain a solute therein.
Further, as a filter used for the purpose of dust collection, there is used a fabric such as a textile (a woven or knitted cloth) or a nonwoven fabric, a three-dimensionally assembled fiber structure, and others. The filter is considered to have higher performance as the filter has lower pressure loss and higher dust collection efficiency. In general, improvement of dust collection efficiency can be achieved to some extent by increasing a fiber density in the fabric or fiber structure, while the high fiber density results in a lower air permeability. Therefore, in order to ensure the air permeability in excess of a certain level to function as a filter, the dust collection efficiency is restricted.
In order to improve the dust collection efficiency while ensuring the air permeability in excess of a certain level, it is effective that the diameter of the fiber constituting the filter is small, and various filters using an ultra-fine fiber have been proposed. Moreover, it is also utilized to collect dust by electrostatic force. There has been utilized a meltblown nonwoven fabric made from an ultra-fine fiber, which is subjected to electreting for collecting dust through electrostatic induction by electrizing a filter itself. However, this electreting tends to neutralize the effect after exposure under a high temperature not lower than 50° C. or after a long time. Therefore, the filter had a propensity to be lack of washing resistance and durability.
Moreover, a method of collecting dust by a scrubber for water sprinkling has been also generally used. For example, a method for collecting dust by combination of a bag filter and a scrubber has been adopted for an incinerator flue gas. In a fine particle having a particle size of not larger than several micrometers, generally, a liquid bridging force is more dominant than an electrostatic force for the adherence of the fine particles. Thus, the scrubber utilizes effective collection of the fine particle due to the liquid bridging force of water.
As an example that the liquid bridging force is utilized for a filter itself, there is utilized a filter improved in a dust collection efficiency thereof, which comprises a fiber structure impregnated with a low-volatile oil component, wherein the fiber structure comprises staple fibers entangled by needle punch or others. However, the filter is limited to such a loose clearance one having a high air permeability that the oil component to be impregnated does not inhibit the air permeability.
Moreover, a fabric for a clean room wear has been proposed which comprises a fiber made from a polymer having a hydrous inorganic compound kneaded therein and has an improved dust collection efficiency with maintaining a relatively high air permeability by slightly coating the surface of the fiber with water (Patent Document 6). However, the high dust collection efficiency is limited to the case of an air flow rate as low as 0.09 cm/second. Therefore, in the case of a commonly used air filter having an air flow rate of 5 to 8 cm/second, an excellent dust collection efficiency cannot be expressed.
Patent Document 1: Japanese Patent Application Laid-Open No. S58-12654
Patent Document 2: Japanese Patent Application Laid-Open No. H10-87920
Patent Document 3: Japanese Patent Application Laid-Open No. S49-53924
Patent Document 4: Japanese Patent Application Laid-Open No. S49-92178
Patent Document 5: Japanese Patent Application Laid-Open No. H06-316031
Patent Document 6: Japanese Patent Application Laid-Open No. 2004-360161